Generally, in order to manufacture a semiconductor integrated circuit, various kinds of heat treatment, such as a film deposition process, an annealing process, an oxidization diffusion process, a sputtering process, an etching process and a nitriding process may be performed on a silicon substrate such as a semiconductor wafer a plurality of times.
Since yield rate and quality of semiconductor manufacturing processes can be improved, the RTP technology to raise and lower the temperature of the wafer (object to he processed) has attracted attention. A conventional RTP apparatus generally comprises: a single-wafer chamber (process chamber) for accommodating an object (for example, a semiconductor wafer, a glass substrate for photograph masks, a glass substrate for a liquid-crystal display or a substrate for optical disks) to be processed; a quartz window disposed in the process chamber; heating lamps (for example, halogen lamps) arranged above or above and under the quartz window; and a reflector (reflective board) arranged at the opposite side of the object to be processed with respect to the quartz window.
The reflector is made of aluminum, for example, and gold plating is typically given to a reflective part thereof. A cooling mechanism (a cooling pipe, etc.) is provided so as to prevent thermal cracking breakage of the reflector (for example, exfoliation of gold plating due to a high temperature) and also to prevent the reflector from being an obstacle to cooling the object to be processed at the time of cooling.
Rapid temperature rising required for the RTP technology depends on power density of the lamp and directivity of a light irradiation from the lamp. The directivity and energy efficiency of the lamp become maximum against the object to be processed provided below when an inclination angle α of the reflector 4 is 45 degrees as shown in FIG. 1, in a case of a single end lamp 2 having one electrode 3 like a valve. Here, FIG. 1 is a cross sectional view for explaining the inclination angle of the reflector 4 when the directivity and the energy efficiency are best, in a case where the object to be processed that is provided below is heated by a radiation light of the single end lamp 2.
The quartz window may be in the shape of a board or in the shape of a pipe where the object to be processed is arranged inside thereof. When a negative pressure environment in the process chamber is maintained by evacuating gasses in the process chamber by a vacuum pump, the quartz window has a thickness of several tens of millimeters (for example, 30 to 40 mm) so as to maintain the pressure difference between the internal pressure and the atmospheric pressure. The quartz window may be formed in a pressure-resistant curved shape having a reduced thickness so as to prevent generation of a thermal stress due to temperature difference generated by a temperature rise.
A plurality of halogen lamps are arranged so as to uniformly heat the object to be processed, and the reflector reflects the infrared rays irradiated from the halogen lamps toward the object to be processed. The process chamber is typically connected to a gate valve on a sidewall thereof so as to carry in and out the object to be processed, and is also connected to a gas supply nozzle at the sidewall for introducing a process gas used for heat treatment.
Since the temperature of the object to be processed affects the quality of process (for example, the thickness of a film in a film deposition process, etc.), it is necessary to know the correct temperature of the object to be processed. In order to attain high-speed heating and high-speed cooling, a temperature measuring device which measures the temperature of the object to be processed is provided in the process chamber. Although the temperature measuring device can be constituted by a thermocouple, there is a possibility of the processed body becoming polluted with the metal which constitutes the thermocouple since it is necessary to bring the thermocouple into contact with the object to be processed. Therefore, there is proposed a pyrometer as a temperature measuring device which detects an infrared intensity emitted and computes the temperature of an object to be processed from the back side thereof based on the detected infrared intensity. The pyrometer computes the temperature of the object to be processed by carrying out a temperature conversion by a rate of radiation of the object to be processed according to the following equation 1:Em(T)=εEBB  (EQUATION 1)
In the above mentioned equation 1, EBB(T) expresses a radiation intensity from a black body having the temperature T; Em(T) expresses a radiation intensity measured from the object to be processed having the temperature T; and ε expresses a rate of radiation of the object to be processed.
In operation, the object to be processed is introduced into the process chamber through the gate valve, and the peripheral portion of the object to be processed is supported by a holder. At the time of heat treatment, process gases such as nitrogen gas and oxygen gas are introduced into the process chamber through the gas supply nozzle. On the other hand, the infrared ray irradiated from the halogen lamps is absorbed by the object to be processed, thereby, raising the temperature of the object to be processed.
However, according to the conventional method of temperature measurement for the object to be processed defined by the above mentioned equation 1, there is an error of approximately 20 through 40 degrees centigrade as compared with an actual temperature of the object to be processed. Hence, there is a disadvantage of the conventional method of temperature measurement in that heat treatment with a high quality cannot be implemented. Inventors of the present application studied reasons for this advantage diligently and realized the following points. That is, in a case where the equation 1 is applied to the temperature measurement of the actual object to be processed, some errors should be considered, and the radiation light from the object to be processed is multiplex-reflected at a surface facing to the object to be processed so that some of these errors are caused. Particularly, there is a big influence of the measurement error due to the multiplex-reflection in a single-wafer process chamber having a large reflectivity of members situated at periphery of the object to be processed for improving heat efficiency.